U.S. patent application number 10/902485 was filed with the patent office on 2006-02-02 for exhaust gas recirculation system having an electrostatic precipitator.
Invention is credited to Matthew Thomas Kiser, Anthony Clark Rodman, David Michael Thaler, Matthew Earnest Williams.
Application Number | 20060021327 10/902485 |
Document ID | / |
Family ID | 35730589 |
Filed Date | 2006-02-02 |
United States Patent
Application |
20060021327 |
Kind Code |
A1 |
Kiser; Matthew Thomas ; et
al. |
February 2, 2006 |
Exhaust gas recirculation system having an electrostatic
precipitator
Abstract
An exhaust gas recirculation system for a power source, has at
least one inlet port configured to receive at least a portion of a
flow of exhaust produced by the power source. The exhaust gas
recirculation system also has an electrode disposed upstream of the
at least one inlet port and configured to charge particulate matter
in the flow of exhaust. The exhaust gas recirculation system
further has at least one collection surface configured to allow the
at least one electrode to repel the charged particulate matter away
from the at least one inlet port towards the at least one
collection surface.
Inventors: |
Kiser; Matthew Thomas;
(Chillicothe, IL) ; Thaler; David Michael;
(Mossville, IL) ; Rodman; Anthony Clark;
(Chillicothe, IL) ; Williams; Matthew Earnest;
(East Peoria, IL) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
35730589 |
Appl. No.: |
10/902485 |
Filed: |
July 30, 2004 |
Current U.S.
Class: |
60/278 ;
60/280 |
Current CPC
Class: |
F02M 26/36 20160201;
F02M 26/15 20160201; F02M 26/50 20160201; F02M 26/06 20160201; F02B
37/00 20130101 |
Class at
Publication: |
060/278 ;
060/280 |
International
Class: |
F02M 25/06 20060101
F02M025/06; F01N 5/04 20060101 F01N005/04 |
Claims
1. An exhaust gas recirculation system for a power source,
comprising: at least one inlet port configured to receive at least
a portion of a flow of exhaust produced by the power source; an
electrode disposed upstream of the at least one inlet port and
configured to charge particulate matter in the flow of exhaust; and
at least one collection surface configured to allow the electrode
to repel the charged particulate matter away from the at least one
inlet port toward the at least one collection surface.
2. The exhaust gas recirculation system of claim 1, wherein the
power source includes an air induction system and the exhaust gas
recirculation system further includes at least one discharge port
in fluid communication with the at least one inlet port, the at
least one discharge port configured to direct the at least a
portion of the flow of exhaust into the air induction system.
3. The exhaust gas recirculation system of claim 2, wherein the air
induction system includes at least one compressor and the at least
one discharge port is fluidly connected to the air induction system
upstream of the at least one compressor.
4. The exhaust gas recirculation system of claim 2, wherein the air
induction system includes at least one venturi and the at least one
discharge port is fluidly connected to the at least one
venturi.
5. The exhaust gas recirculation system of claim 2, further
including a valve disposed between the at least one inlet port and
the at least one discharge port, the valve configured to regulate
the flow of the at least a portion of the flow of exhaust.
6. The exhaust gas recirculation system of claim 1, wherein the
power source includes at least one turbine, the at least one inlet
port being configured to receive the at least a portion of the flow
of exhaust downstream from the at least one turbine.
7. The exhaust gas recirculation system of claim 1, further
including a means for electrically insulating the at least one
electrode.
8. The exhaust gas recirculation system of claim 7, further
including a fluid passageway configured to direct a flow of shield
gas past at least one of the means for insulating and the at least
one electrode.
9. The exhaust gas recirculation system of claim 8, wherein the
power source includes an air induction system and the fluid
passageway is fluidly connected to the air induction system.
10. The exhaust gas recirculation system of claim 9, wherein the
air induction system includes at least one air filter and the fluid
passageway is configured to receive the flow of shield gas from the
air induction system downstream of the at least one air filter.
11. The exhaust gas recirculation system of claim 8, wherein the
power source includes at least one venturi through which the flow
of exhaust is directed, and the fluid passageway is fluidly
connected to the at least one venturi.
12. The exhaust gas recirculation system of claim 8, wherein the
power source includes an air induction system having an air source
and an auxiliary air source separate from the air induction system,
the flow of shield gas being supplied by the auxiliary air
source.
13. A method of operating an exhaust gas recirculation system for a
power source, the method comprising: charging particulates
entrained within an exhaust flow produced by the power source with
at least one electrode; receiving at least a portion of the exhaust
flow with at least one inlet port; repelling the charged
particulates away from the at least inlet port towards at least one
collection surface; and directing the at least a portion of the
exhaust flow to an air induction system of the power source.
14. The method of claim 13, wherein repelling the charged
particulates includes repelling the charged particulates away from
the at least a portion of the exhaust flow upstream of the at least
one inlet port.
15. The method of claim 13, wherein the air induction system
includes at least one compressor and the at least a portion of the
exhaust flow is directed to the air induction system upstream of
the at least one compressor.
16. The method of claim 13, wherein the air induction system
includes at least one venturi and the at least a portion of the
exhaust flow is directed to the air induction system via the
venturi.
17. The method of claim 13, further including regulating the flow
of the at least a portion of the exhaust flow.
18. The method of claim 13, wherein the power source includes at
least one turbine and the at least a portion of the exhaust flow is
received downstream of the turbine.
19. The method of claim 13, further including electrically
insulating the at least one electrode.
20. The method of claim 13, further including directing a shield
gas past the at least one electrode.
21. The method of claim 20, wherein the shield gas is directed from
an air induction system of the power source.
22. The method of claim 21, wherein the power source includes at
least one filter, and the shield gas is directed from downstream of
the at least one filter.
23. The method of claim 13, wherein the power source includes at
least one venturi disposed in the exhaust flow, and the at least a
portion of the exhaust flow is received via the venturi.
24. A power system, comprising: a power source having an air
induction system, the power source operable to produce a flow of
exhaust; and an exhaust gas recirculation system in fluid
communication with the flow of exhaust, the exhaust gas
recirculation system including: at least one inlet port configured
to receive at least a portion the flow of exhaust; an electrode
disposed upstream of the at least one inlet port and configured to
charge particulate matter in the flow of exhaust; a means for
electrically insulating the at least one electrode; at least one
collection surface configured to allow the at least one electrode
to repel the charged particulate matter away from the at least one
inlet port; at least one discharge port in fluid communication with
the at least one inlet port, the at least one discharge port
configured to direct the at least a portion of the flow of exhaust
into the air induction system; and a valve disposed between the at
least one inlet port and the at least one discharge port, the valve
configured to regulate the flow of the at least a portion of the
flow of exhaust.
25. The power system of claim 24, wherein the air induction system
includes at least one compressor, and the at least one discharge
port is fluidly connected to the air induction system upstream of
the at least one compressor.
26. The power system of claim 24, wherein the air induction system
includes at least one venturi, and the at least one discharge port
is fluidly connected to the venturi.
27. The power system of claim 24, wherein the power source includes
at least one turbine, and the at least one inlet port is configured
to receive the at least a portion of the flow of exhaust downstream
from the at least one turbine.
28. The power system of claim 24, further including a fluid
passageway configured to direct a flow of shield gas past at least
one of the means for insulating and the at least one electrode.
29. The power system of claim 28, wherein the air induction system
includes at least one air filter, and the fluid passageway is
configured to receive the flow of shield gas from the air induction
system downstream of the at least one filter.
30. The power system of claim 28, wherein the power source includes
at least one venturi through which the flow of exhaust is directed,
wherein the fluid passageway is fluidly connected to the at least
one venturi.
31. A gas handling system, comprising: an inlet; an outlet in fluid
communication with the inlet; one or more process components
disposed between the inlet and the outlet; at least one electrode
disposed between the inlet and the outlet, the at least one
electrode configured to charge particulates in a flow gas between
the inlet and the outlet; and at least one collecting surface
configured to allow the at least one electrode to repel the charged
particulates away from the one or more process components.
32. The gas handling system of claim 31, wherein the at least one
collecting surface includes grounded walls of a fluid
passageway.
33. The gas handling system of claim 31, further including a shield
gas passageway configured to direct a flow of shield gas past the
at least one electrode.
34. A method of operating a gas handling system having one or more
process components, comprising: directing a flow of gas from an
inlet towards the one or more process components; charging
particulates within the flow of gas with at least one electrode;
and electrically repelling the charged particulates away from the
one or more process components towards at least one collecting
surface.
35. The method of claim 34, further including directing a flow of
shield gas past the at least one electrode.
Description
TECHNICAL FIELD
[0001] The present disclosure relates generally to an exhaust gas
recirculation system and, more particularly, to an exhaust gas
recirculation system having an electrostatic precipitator.
BACKGROUND
[0002] Internal combustion engines, including diesel engines,
gasoline engines, natural gas engines, and other engines known in
the art, may exhaust a complex mixture of air pollutants. The air
pollutants may be composed of gaseous compounds, which may include
nitrous oxides (NOx), and solid particulate matter, which may
include unburned carbon particulates called soot.
[0003] Due to increased attention on the environment, exhaust
emission standards have become more stringent. The amount of
gaseous compounds emitted to the atmosphere from an engine may be
regulated depending on the type of engine, size of engine, and/or
class of engine. One method that has been implemented by engine
manufacturers to comply with the regulation of these engine
emissions has been to implement exhaust gas recirculation (EGR).
EGR systems recirculate the exhaust gas by-products into the intake
air supply of the internal combustion engine. The exhaust gas,
which is redirected to the engine cylinder, reduces the
concentration of oxygen therein, which in turn lowers the maximum
combustion temperature within the cylinder. The lowered maximum
combustion temperature slows the chemical reaction of the
combustion process, thereby decreasing the formation of nitrous
oxides.
[0004] In many EGR applications, the exhaust gas is diverted
directly from the exhaust manifold by an EGR valve. However, the
particulate matter in the recirculated exhaust gas can adversely
affect the performance and durability of the internal combustion
engine. As disclosed in U.S. Pat. No. 6,526,753 (the '753 patent),
issued to Bailey on Mar. 3, 2003, a filter can be used to remove
particulate matter from the exhaust gas that is being fed back to
the intake air stream for recirculation. Specifically, the '753
patent discloses an exhaust gas regenerator/particulate capture
system that includes a first particulate trap and a second
particulate trap. A regenerator valve operates between a first
position where an EGR inlet port fluidly connects a portion of an
exhaust flow with the first particulate trap and a second position
where the EGR inlet port fluidly connects the portion of the
exhaust flow with the second particulate trap. The filtered EGR
gases are then supplied for mixing with compressed air prior to or
during entry into the intake manifold.
[0005] Although the exhaust gas regenerator/particulate capture
system of the '753 patent may reduce the engine air pollutants
exhausted to the environment while protecting the engine from
harmful particulate matter, the exhaust gas regenerator/particulate
capture system may be expensive and difficult to package. For
example, because the exhaust gas regenerator/particulate capture
system of the '753 patent must draw exhaust downstream of the first
and second particulate traps and provide the recirculated exhaust
flow to the intake manifold upstream of the engine, it may be large
and awkward with extensive lengths of piping. This size coupled
with the space required within the engine compartment to
accommodate the exhaust gas regenerator/particulate capture system
increases the cost of the exhaust gas regenerator/particulate
capture system and the difficulty of retrofitting the exhaust gas
regenerator/particulate capture system to older vehicles. In
addition, the extensive lengths of piping and large particulate
filters may create problematic flow restrictions.
[0006] The disclosed exhaust gas recirculation system is directed
to overcoming one or more of the problems set forth above.
SUMMARY OF THE INVENTION
[0007] In one aspect, the present disclosure is directed to an
exhaust gas recirculation system for a power source that includes
at least one inlet port configured to receive at least a portion of
a flow of exhaust produced by the power source. The exhaust gas
recirculation system also includes an electrode disposed upstream
of the at least one inlet port and configured to charge particulate
matter in the flow of exhaust. The exhaust gas recirculation system
further includes at least one collection surface configured to
repel the charged particulate matter away from the at least one
inlet port towards the at least one collection surface.
[0008] In another aspect, the present disclosure is directed to a
method of operating an exhaust gas recirculation system. The method
includes charging particulates entrained within an exhaust flow
produced by the power source with at least one electrode. The
method also includes receiving at least a portion of the exhaust
flow with at least one inlet port and repelling the charged
particulates away from the at least one inlet port towards at least
one collection surface. The method further includes directing the
at least a portion of an exhaust flow to an air induction system of
the power source.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a diagrammatic illustration of an engine having an
exhaust gas recirculation system according to an exemplary
disclosed embodiment;
DETAILED DESCRIPTION
[0010] FIG. 1 illustrates a power source 10 having an exemplary
exhaust gas recirculation (EGR) system 12. Power source 10 may
include an engine such as, for example, a diesel engine, a gasoline
engine, a natural gas engine, or any other engine apparent to one
skilled in the art. Power source 10 may also include other sources
of power, such as a furnace or any other source of power known in
the art. Power source 10 may include an air induction system 14 and
an exhaust system 16.
[0011] Air induction system 14 may be configured to introduce
compressed air into a combustion chamber (not shown) of power
source 10. Air induction system 14 may include an air filter 18, a
venturi 20, and a compressor 22.
[0012] Air filter 18 may be configured to remove or trap debris
from air flowing into power source 10. Air filter 18 may include
any type of air filter such as, for example, a full-flow filter, a
self-cleaning filter, a centrifuge filter, an electro-static
precipitator, or any other air filter known in the art. It is
contemplated that more than one air filter 18 may be included
within air induction system 14 and disposed in series or parallel
relation.
[0013] Venturi 20 may be configured to constrict the flow of air
within air induction system 14, thereby increasing a speed of the
fluid passing through venturi 20 and, in turn, reducing a pressure
of the flow of air through the constriction. Venturi 20 may be
fluidly connected to air filter 18 via fluid passageway 24. It is
contemplated that additional venturis may be included within air
induction system 14. It is also contemplated that venturi 20 may be
omitted, if desired, and a throttle valve (not shown) implemented
instead.
[0014] Compressor 22 may be configured to compress the air flowing
into power source 10 to a predetermined pressure when compressor 22
operates. Compressor 22 may be fluidly connected to venturi 20 via
fluid passageway 26. Compressor 22 may include a fixed geometry
type compressor, a variable geometry type compressor, or any other
type of compressor known in the art. It is contemplated that more
than one compressor 22 may be included and disposed in parallel or
in series relationship. It is further contemplated that compressor
22 may be omitted, for example, when a non-compressed air induction
system is desired.
[0015] Exhaust system 16 may be configured to direct exhaust flow
out of power source 10. Exhaust system 16 may include a turbine 28,
a venturi 30, and an exhaust outlet 32. It is contemplated that
additional emission controlling devices may be included within
exhaust system 16 such as, for example, particulate filters,
catalysts, and other emission controlling devices known in the
art.
[0016] Turbine 28 may be connected to compressor 22 and configured
to drive compressor 22. In particular, as the hot exhaust gases
exiting power source 10 expand against the blades (not shown) of
turbine 28, turbine 28 may be caused to rotate, thereby rotating
connected compressor 22. It is contemplated that more than one
turbine 28 may be included within exhaust system 16 and disposed in
parallel or in series relationship. It is also contemplated that
turbine 28 may alternately be omitted and compressor 22 driven by
power source 10 mechanically, hydraulically, electrically, or in
any other manner known in the art.
[0017] Venturi 30 may be configured to constrict the exhaust
flowing out of power source 10, thereby causing the pressure of the
exhaust flow to drop within venturi 30. Venturi 30 may be connected
to turbine 28 via fluid passageway 33. It is contemplated that more
than one venturi may be included within exhaust system 16.
[0018] Exhaust outlet 32 may be connected to venturi 30 via fluid
passageway 34 and configured to direct the exhaust flow from power
source 10 to the atmosphere. Fluid passageway 34 may be
electrically grounded. It is contemplated that additional or
different surfaces within exhaust system 16 may be electrically
grounded.
[0019] EGR system 12 may be configured to redirect a portion of the
exhaust flow of power source 10 from exhaust system 16 into air
induction system 14. EGR system 12 may include an inlet port 36, an
EGR valve 38, a discharge port 40, an electrostatic precipitator
device 42, and a shield gas passageway way 44. It is contemplated
that EGR system 12 may include additional components such as, for
example, an EGR gas cooler, additional valve mechanisms, valve
driving mechanisms, a control system, an oxidation catalyst, and
other EGR components known in the art.
[0020] Inlet port 36 may be connected to exhaust system 16 and
configured to receive at least a portion of the exhaust flow from
power source 10. Specifically, inlet port 36 may be disposed
between venturi 30 and exhaust outlet 32 downstream from turbine
28. Inlet port 36 may be insulated from grounded portions of EGR
system 12 and Exhaust system 16. It is contemplated that inlet port
36 may be located elsewhere within exhaust system 16.
[0021] EGR valve 38 may be fluidly connected to inlet port 36 via
fluid passageway 46 and configured to regulate the flow of the
fluid through inlet port 36. EGR valve 38 may be a spool valve, a
shutter valve, a butterfly valve, a check valve, a diaphragm valve,
a gate valve, a shuttle valve, a ball valve, a globe valve, or any
other valve known in the art. EGR valve 38 may be electrically
actuated, hydraulically actuated, pneumatically actuated, or
actuated in any other manner. EGR valve 38 may be in communication
with a controller (not shown) and selectively actuated in response
to one or more predetermined conditions.
[0022] Discharge port 40 may be fluidly connected to EGR valve 38
via fluid passageway 48 and configured to direct the exhaust flow
regulated by EGR valve 38 into air induction system 14.
Specifically, discharge port 40 may be connected to venturi 20,
wherein the low pressure of the air flowing through venturi 20
draws the exhaust flow from discharge port 40.
[0023] Electrostatic precipitator device 42 may include an
electrically insulated electrode 50 configured to charge
particulate matter entrained within the exhaust flow produced by
power source 10 before the particulates reach inlet port 36.
Electrode 50 may extend from shield gas passageway 44 into fluid
passageway 34 to substantially co-axially align with inlet port 36.
It is contemplated that electrode 50 may extend a portion of a
distance into inlet port 36. Electrode 50 may be selectively
connected to a high-voltage source (not shown) to create an
ionizing atmosphere around electrode 50, as voltage is applied to
electrode 50. The voltage applied to electrode 50 may range from
5,000 volts to 30,000 volts or higher, with a preferred range of
7,500 volts to 20,000 volts. It is contemplated that more than one
electrode 50 may be associated with electrostatic precipitator
device 42 and that electrode 50 may alternately be connected to a
fluid passageway of exhaust system 16, rather than shield gas
passageway 44. It is further contemplated that the voltage applied
to electrode 50 may be higher than 20,000 volts without causing
spark-over. It is further contemplated that the voltage applied to
electrode 50 may be varied in response to one or more inputs such
as, for example, engine speed, engine load, temperature, pressure,
or any other engine operating condition.
[0024] Electrode 50 may be electrically insulated from shield gas
passageway 44 via insulating means 52. Insulating means 52 may be
any means for electrically insulating electrode 50 from shield gas
passageway 44 such as, for example, a sleeve positioned between
electrode 50 and the walls of shield gas passageway 44 made from an
electrically non-conductive material such as, for example, a
ceramic, a high-temperature plastic, a fibrous composite, or any
other means known in the art. Insulating means 52 may be connected
to a wall of shield gas passageway 44.
[0025] Shield gas passageway 44 may be configured to supply inlet
air past electrode 50 and insulating means 52. The flow of air
minimizes the amount of particulate matter that travels upstream
within shield gas passageway 44 and deposits on electrode 50 and
insulating means 52. Particulate matter buildup on either of
electrode 50 and insulating means 52 may lead to arcing and fouling
within electrostatic precipitator device 42. Shield gas passageway
44 may extend from fluid passageway 24 between venturi 20 and air
filter 18 to venturi 30 of exhaust system 16. The low pressure
within exhaust system 16 caused by venturi 30 may draw the
non-compressed air into exhaust system 16. It is contemplated that
shield gas passageway 44 may alternately be connected downstream of
compressor 22, within air induction system 14, to provide a
pressurized source of shield gas to prevent arcing or fouling of
electrostatic precipitator device 42. It is also contemplated that
a source of pressurized air other than compressor 22 may be
included within EGR system 12.
INDUSTRIAL APPLICABILITY
[0026] The disclosed EGR system may be applicable to any
combustion-type device such as, for example, an engine, a furnace,
or any other device known in the art where the recirculation of
substantially particulate-free exhaust gas into an air induction
system is desired. EGR system 12 may be a simple, inexpensive, and
compact solution to reducing the amount of exhaust emissions
discharged to the environment while protecting the combustion-type
device from harmful particulate matter and poor performance caused
by particulate matter. The operation of EGR system 12 will now be
explained in detail.
[0027] Atmospheric air may be drawn into air induction system 14
via air filter 18 and directed through fluid passageway 24, venturi
20, and fluid passageway 26 to compressor 22 where it is
pressurized to a predetermined level before entering the combustion
chamber of power source 10. Fuel may be mixed with the air prior to
or after entering the combustion chamber. This fuel-air mixture may
then be combusted by power source 10, thereby producing mechanical
work and an exhaust flow containing gaseous compounds and solid
particulate matter. The discharge of exhaust from the combustion
chamber coupled together with the expansion of the hot exhaust
gasses may cause turbine 28 to rotate and drive compressor 22.
[0028] After exiting turbine 28, the exhaust gases may be directed
through fluid passageway 33 and venturi 30 and past electrode 50 of
electrostatic precipitator device 42. As the exhaust flows from
power source 10, voltage may be applied to electrode 50 causing
electrode 50 to emit electrons thereby creating an ionizing field.
This ionizing field may charge particulate matter that is entrained
within the exhaust flow as the particulate matter enters the
ionizing field. In order to minimize the particulate matter
entrained within the exhaust flow from adhering to electrode 50 and
causing arcing or fouling, air may be drawn from shield gas
passageway 44 past electrode 50 and insulating means 52 by the low
pressure exhaust flow created by venturi 30.
[0029] Simultaneous to charging the particulate matter, the walls
of fluid passageway 34 may be electrically grounded, thereby
allowing the ionizing field to electrostatically repel the charged
particulate matter towards the grounded walls of fluid passageway
34. This electrostatic repelling action may cause the charged
particulate matter to migrate away from inlet port 36 toward the
grounded walls of fluid passageway 34. This repelling action may
provide a zone of substantially particulate-free exhaust gas
immediately upstream of inlet port 36, thereby decreasing the
amount of particulate matter entrained within the portion of the
exhaust flow received by inlet port 36.
[0030] The flow of the substantially particulate-free portion of
the exhaust flow received by inlet port 36 may be regulated by EGR
valve 38 and drawn back into air induction system 14 by the low
pressure inlet air flow created by venturi 20. The recirculated
exhaust flow may then be mixed with the air entering the combustion
chamber. As described above, the exhaust gas, which is directed to
the combustion chamber, reduces the concentration of oxygen
therein, which in turn lowers the maximum combustion temperature
within the cylinder. The lowered maximum combustion temperature
slows the chemical reaction of the combustion process, thereby
decreasing the formation of nitrous oxides. In this manner, the
gaseous pollution produced by power source 10 may be reduced
without experiencing the harmful effects and poor performance
caused by particulate matter being introduced into power source 10
via EGR system 12.
[0031] Because the exhaust gas recirculated through air induction
system 14 may be drawn from a point immediately downstream from
turbine 28, the length of piping within EGR system 12 may be kept
to a minimum, thereby decreasing flow restriction within EGR system
12. The short length of piping may allow for a compact system that
is easily retrofitted to existing power systems. In addition, the
compact size minimizes overall system cost.
[0032] It will be apparent to those skilled in the art that various
modifications and variations can be made to the disclosed EGR
system. Other embodiments will be apparent to those skilled in the
art from consideration of the specification and practice of the
disclosed EGR system. For example, rather than diverting exhaust
gas from downstream of turbine 28 to upstream of compressor 22, the
exhaust gas may be diverted from upstream of turbine 28 to a point
downstream of compressor 22. It is also contemplated that EGR
system 12 may function by using only naturally occurring charges
within the particulate matter rather than applying a voltage to
cause charging of the particulate matter. Further, electrostatic
precipitator device 42 may divert solid particulate matter away
from one or more exhaust system process components other than an
EGR inlet port. These process components may include, for example,
a turbine, a catalyst, a valve, or any other process components
known in the art. It is further contemplated that electrostatic
precipitator device 42 may be included in an air handling system
that is not associated with an exhaust system, and used to divert
charged particulates away from critical components of the air
handling system. It is intended that the specification and examples
be considered as exemplary only, with a true scope being indicated
by the following claims and their equivalents.
* * * * *